Field of the Invention
The present invention relates to a magnetic memory.
Priority is claimed on Japanese Patent Application No. 2016-020598, filed on Feb. 5, 2016, the content of which is incorporated herein by reference.
Description of Related Art
Gigantic magnetoresistance (GMR) elements formed of a multilayer film consisting of a ferromagnetic layer and a non-magnetic layer, and tunnel magnetoresistance (TMR) elements using an insulating layer (a tunnel barrier layer or a barrier layer) as a non-magnetic layer have been known. In general, TMR elements have higher element resistance than GMR elements, but a magnetoresistance (MR) ratio of the TMR elements is higher than that of the GMR elements. Therefore, TMR elements have attracted attention as an element for a magnetic sensor, a high-frequency component, a magnetic head, or a magnetoresistive random access memory (MRAM).
In an MRAM, data is written using the following properties: in a case where magnetization directions of two ferromagnetic layers between which an insulating layer is interposed change, an element resistance of TMR elements changes. As a write method for an MRAM, methods such as writing data (magnetization reversal) using a magnetic field generated by current, and writing data (magnetization reversal) using spin-transfer torque (STT) generated by current flowing in a laminating direction of magnetoresistance elements are known.
Incidentally, it is known that the coercive force of a ferromagnetic layer depends on the temperature of the ferromagnetic layer. As the temperature of a ferromagnetic layer increases, the coercive force of a ferromagnetic body decreases. Therefore, a general MRAM is designed such that data can be written (magnetization reversal) even at a low temperature at which the coercive force is high, and such that data can be held (no magnetization reversal) even at a high temperature at which the coercive force is low.
Typically, the guarantee temperature of a commercially available product is set to be wider than an assumed temperature at which the product is assumed to be used. Therefore, in an MRAM which is designed and prepared as described above, the write efficiency during actual use may be insufficient. Therefore, in order to compensate for a change in coercive force depending on a temperature change, Japanese Unexamined Patent Application, First Publication No. 2004-95157, Japanese Unexamined Patent Application, First Publication No. 2004-326951, and Japanese Unexamined Patent Application, First Publication No. 2005-322352 disclose memory elements in which the temperature of a magnetoresistance element is measured using a temperature sensor to change the amount of an applied current depending on the temperature.